Machine for inspecting glass containers at an inspection station using an addition of a plurality of illuminations of reflected light

ABSTRACT

A machine for inspecting glass containers which are being rotated at an inspection station. A light source illuminates a selected area on a rotating glass container while the container rotates through a selected angle and a camera is triggered to capture an image while the bottle rotates through that angle. A plurality of sequential images are recorded and a critical addition is made to be inspected.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional patent application of U.S.patent application Ser. No. 11/585,388, filed on Oct. 23, 2006 now U.S.Pat. No. 7,816,639, entitled “Machine For Inspecting Glass Containers AtAn Inspection Station Using An Addition Of A Plurality Of IlluminationsOf Reflected Light,” which patent application is assigned to theassignees of the present invention and which is hereby incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to machines, which inspect glasscontainers for defects, and more particularly, to a system whichinspects for cracks in translucent glass containers.

In the glass container industry, small cracks or fracture in the glassare referred to as “check defects. Checks can range from sub millimetersto several hundred millimeters and can be oriented at any direction fromvertical to horizontal. Glass is not a crystalline structure by nature,but most cracks propagate roughly along a plane of some orientation inspace mostly determined by the shape of the glass at that location. Forexample, a crack that began as a vertical crack at the upper surface ofthe mouth primarily propagates in a vertical plane. Checks can appear inany orientation and on any portion of a container and can exist whollywithin the glass or may penetrate to one or both surfaces. Checks areconsidered phase objects and do not absorb light like a solid objectsdoes. Checks are primarily reflective in nature if their opposed surfaceseparation is at least half a wavelength of light. However, very fewchecks with a smaller separation will reflect light and accordingly theywill not likely be detectable by direct reflection methods, but theymight have scattering points when they penetrate to the one or bothsurfaces of the container and will scatter light back to the sensors.

Most of these crack defects will drastically weaken the bottle, oftencausing it to rupture or to leak. Therefore, bottle manufacturers liketo remove these containers before they reach filling plants. Checksappearing near the mouth of the containers are called finish checks. Inthe glass bottle industry, the term “container finish” refers to theportion of the bottle that defines the mouth, threads or beads, and thering. The upper surface of the mouth is referred as the sealing surface.

Almost all commercially available check detectors work on the principleof reflected light. A conventional check detector consists of a seriesof continuously operating light spot light sources and associatedphotodetectors that are positioned so that known checks on a bottlerotating at an inspection station will reflect light from one of thesources to one of the photo-detectors. Signal processing of thephotodetector outputs recovers the sharp peaks while rejecting lowerfrequency signal variations caused by ambient light, reflection from thebottle sidewall, etc.

While commercially available check detectors are successfully deployedon most glass bottle production lines, there are several drawbacks tothe approach. A few of those are: many point sensors are required formany possible reflection angles; some sensor angles are difficult toposition; additional sensors and lights need to be added as moreproduction defects appear; time consuming setup is required for eachtype of container; and the difficulty of reproducing the same setup fromone inspection line to another.

The following U.S. Pat. No. 4,701,612, to Sturgill; U.S. Pat. No.4,945,228, to Juvinall et al.; U.S. Pat. No. 4,958,223, to Juvinall etal.; U.S. Pat. No. 5,020,908, to Hermann; U.S. Pat. No. 5,200,801, toJuvinall et al.; U.S. Pat. No. 5,895,911, to Giometti et al.; U.S. Pat.No. 6,104,482, to Brower et al.; U.S. Pat. No. 6,211,952, to Weiland etal.; and U.S. Pat. No. 6,275,287, to Watanabe all relate to devices thatdetect defects in the finish of a container.

SUMMARY OF THE INVENTION

The present invention provides an apparatus for inspecting glasscontainers, which can detect vertical, horizontal, and any other anglecracks on a bottle which is user friendly and easily adjusted. It alsoprovides a detector that can detect known types of checks and also anynew checks without specific setup requirements.

DESCRIPTION OF THE DRAWINGS

The present invention is illustrated in the following accompanyingdrawings which illustrate, in accordance with the mandate of the patentstatutes, a presently preferred embodiment incorporating the principlesof the invention.

FIG. 1 is an oblique elevational schematic view of an inspection stationof a machine for inspecting glass containers for checks and otherdefects, made in accordance with the teachings of the present invention;

FIG. 2 is a block diagram showing the operation of the pairs of lightsources and camera shown in FIG. 1;

FIG. 3 is a schematic top view of the container at the inspectionstation showing the light axes of a pair of light sources and thecamera;

FIG. 4 is a schematic elevational view showing the light axes of thelight sources and camera shown in FIG. 3;

FIG. 5 is a logic diagram illustrating the operation of the camerasystem of the inspection machine;

FIG. 6 is a logic diagram illustrating the operation of the lightingsystem of the inspection machine;

FIG. 7 is a timing diagram illustrating the operation of the lightsources;

FIG. 8 is a side elevational view of one of the light sources; and

FIG. 9 is an elevational view showing how the LED's of one of the lightsources are aimed toward the finish.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT

In a machine for inspecting glass containers (bottles), the containers10 are transported along a conveyor 12 to an inspection stationillustrated in FIG. 1. The conveyor may be a linear belt or a turrettype feed system. A container 10 is engaged by upper and lower rearpairs of idler rollers 14 and a front drive wheel 16 so that rotation ofthe drive wheel in the clockwise direction will rotate the container inthe counterclockwise direction. There is conveyor dwell of sufficientduration at the inspection machine so that the container can be rotatedmore than 360 degrees while the inspection takes place. A containerpresent sensor 18 will sense the presence of a container at theinspection station (the sensor can be upstream and the actual presenceof the container at the inspection station could be defined by anencoder count following the sensing of the container by the upstreampart present sensor. Light sources (Light Source #1/20 (see FIGS. 1 and2) and Light Source #2/21) illuminate the finish portion of thecontainer and a Camera/22 images the finish portion.

FIG. 2 illustrates the operation of the Camera and Light Sources. AComputer 24 delivers On/Off signals to Light Source #1/20 and LightSource #2/21 and delivers Camera Trigger signals to the Camera/22. TheCamera has a matrix array of elements (pixels) to receive an image ofthe finish portion of the container during the Camera's exposure period.The Camera could be a CCD, MOS or like camera which will store an imageuntil the next Trigger Signal. When a Trigger Signal is received, theexisting image will be captured and transferred, as an “Acquisition,” tothe Computer so that it can be recorded and processed by the Computer.The Computer will issue a Reject Signal if a defect is identified.

As can be seen from FIGS. 3 and 4, the Light Axis for each light source,which is in the positive “Z” plane of the container, is horizontal andintersects the axis “A” of the container. The two light axes areorthogonal to each other and 45° to a vertical plane including theCamera Detector Axis. The Detector Axis for the Camera/22, which islocated in the negative “Z” plane, is approximately 45° from horizontal.With this relationship, the camera is looking at a dark field and seeingonly light coming from the checks. The light sources and camera aresupported by structure 28 that can be vertically displaced andhorizontally displaced to reposition the system for differentheight/diameter containers.

To start an inspection, the machine will Transfer A Bottle To TheInspection Station/30. Following a time sufficient for the rotation ofthe bottle, by the drive wheel, to become stable, the Computer willTrigger The Camera/32. This starts the acquisition of the image. Thefollowing explanation is provided in terms of angles for purposes ofclarity, but it should be understood that in a digitally controlledcamera, instructions may be time based rather than defining actualangles so that when something is to occur in an approximate θ° (60°angle in the preferred embodiment), an approximate time (number ofpulses) may be selected which approximately corresponds to that angleand where events are desired approximately every 7.5° , for example, thepulses could be divided by 8. When the query “Has Bottle Rotated θ°?”/34(θ° or a selected number of pulses corresponding approximately to thatangle of rotation can be set) is answered in the affirmative, theComputer will Transfer And Record The Acquisition/36 Once the Camera istriggered, the Camera will capture data until the Camera is againtriggered (following the rotation through θ°). When the Computer answersthe query “Y Acquisitions?” in the negative, the Computer will againTrigger The Camera/32. When the computer answers the query “YAcquisitions?”/38 in the affirmative (“Y” may be set and is six in thepreferred embodiment), the Computer will Create An Image From YAcquisitions To be Analyzed/40. The image created (a Critical Addition),where as in the preferred embodiment “Y” is six, will represent theentire (approximately) 360°surface of the finish and will be theCritical Addition of six acquisitions each imaging eight illuminations.

The critical addition will be made in a manner that will maximize thedata that indicates that a defect is present. The Critical Addition canrepresent for each pixel location, the highest intensity of thecorresponding pixel in all six Acquisitions which will make up theCritical Addition. Then, when the Computer answers the inquiry NextBottle?/44 in the affirmative, the next bottle can be processed.

An image processing technique may be used to enhance the signal createdby checks from signal created by mold features of the container. First,a reference or “mask image,” can be created using a set of samplecontainers without defects running through the inspection setup(containers without defects are referred as “good ware” and containerswith defects that need to be removed during the inspection as “badware”). To incorporate all the signals created by good ware fromdifferent molds that may contain slightly different structuralvariations, and small variations of signals due to vibrations androtation, a large number of images can be acquired and processed tocreate the mask image. These images contain almost all the possiblevariation of light reflection by mold marks, threads, seams, and curvedsurface of good ware. Mask image is created by combining the all thegood ware images. A mask image is created and is compared with thereference mask created with good ware. The difference between the imageand the mask shows the signals created by check defects.

FIG. 6 illustrates the operation of the light sources. When the Computeranswers the query “Is Image Acquisition To Begin?”/52 in theaffirmative, the Computer will Turn Lights “On” For Angle “α”/54 (“α”may be set and could be a defined number of pulses). When the Computeranswers the query “Has Container Rotated “φ°”/56 in the affirmative (φcan be set), and answers the query “Has Container Rotated θ° ?”/58 inthe negative, the light sources will again be turned “on.” When thisinquiry is answered in the affirmative (θ/φ pulse per acquisition), andthe query Have “Y” Images Been Acquired?/60,” in the negative the entiresurface has not been imaged and the entire process can be repeated until“Y” images have been acquired (Y pulses per acquisition). Then, when thecomputer answers the inquiry “Has Next Container Been Sensed?”/62 in theaffirmative, the entire process can be repeated for the next bottle. Ifthe lights are to be on for the entire time that the camera is triggered(α can be set to equal θ°).

To reduce noise, α is, in the preferred embodiment, defined so that thesurface will be illuminated a small portion (25%) of the angle φ°.Checks that will cause a container to be rejected have been found to beimaged when the light sources are “on” only a small fraction of a. Thisfraction can be empirically varied to achieve a desired result. Whilethe imaging process has been disclosed with reference to checks in thefinish area of the container, it can be used to identify body or heelchecks and other defects.

FIG. 7 is a timing diagram for an Acquisition comprised of light sourcesturned on ● degrees for every φ° (7.5° in the preferred embodiment)through θ (60° in the preferred embodiment). The lower the ratio ofα/φ°, the less noise will be available to interfere with the desiredsignal.

The light sources 70 (FIGS. 8 and 9) are mirror images and are segmentsof an arc. As shown the light source, mounted on a flat panel 71, isperpendicular to the Light Axis and faces the finish of the container 10which is shown in dotted lines.

The segment has inner and outer (or three or four, . . . ) rows of LED's72 with the central LED's 74, which define the Light Axis, standingparallel to the Light Axis and with the remaining LED's beingprogressively tilted toward the light axis as they proceed away from theLight Axis. The preferred location of the Light Axis is at the sealingsurface 74 but it can be located from the sealing surface to the bottomof the finish. The ideal geometry that the preferred embodiment attemptsto approach is that of conical illumination, where the top and bottom ofthe cone are dark so that the camera will not see any direct reflectionsof light. Viewing the finish as a torus, this conical geometry allowsthe maximum light to be projected onto the finish with directreflection. Only an anomaly in the finish (a check) will generate directreflections to the camera.

This apparatus has following advantages: because the area sensor imagean area of the bottle, it is possible to detect almost all the checks inthat region. This make the inspection is independent of the specificorientation and location of the check, and thus enable detecting “new”checks without changing the setup. The positioning of the area arraysensors and light sources would not depend essentially on the geometryof the bottle. It will be easier to setup for most of the containerswith little or no adjustments.

Although the foregoing description of the present invention has beenshown and described with reference to particular embodiments andapplications thereof, it has been presented for purposes of illustrationand description and is not intended to be exhaustive or to limit theinvention to the particular embodiments and applications disclosed. Itwill be apparent to those having ordinary skill in the art that a numberof changes, modifications, variations, or alterations to the inventionas described herein may be made, none of which depart from the spirit orscope of the present invention. The particular embodiments andapplications were chosen and described to provide the best illustrationof the principles of the invention and its practical application tothereby enable one of ordinary skill in the art to utilize the inventionin various embodiments and with various modifications as are suited tothe particular use contemplated. All such changes, modifications,variations, and alterations should therefore be seen as being within thescope of the present invention as determined by the appended claims wheninterpreted in accordance with the breadth to which they are fairly,legally, and equitably entitled.

1. A method for inspecting a glass container for defects at aninspection station comprising: rotating a selected glass container abouta vertical axis at the inspection station; illuminating a selectedportion of the glass container with first and second light sources sothat defects will be highlighted during the rotation of the glasscontainer, the light sources having a selected illuminated on timefollowed by a selected off time, wherein the container rotates through adefined angle of rotation while the two light sources are successivelyon and off; turning said light sources on and off a plurality ofconsecutive times defining a plurality of illuminations during thedefined angle of rotation, the plurality of illuminations equal to thenumber of times the light sources are turned on and off; imaging theselected illuminated portion of the glass container with a cameraincluding a triggerable imaging portion and including a detector axisinclined to the horizontal, said camera having an exposure time at leastequal to the time required for the glass container to rotate throughsaid defined angle of rotation; and triggering the imaging portion ofsaid camera with a computer when the container is at the beginning andend of said defined angle of rotation so that the camera willcontinuously acquire data of said selected portion of the container, asthe glass container rotates through the defined angle of rotation tocapture, transfer, and record each image when the imaging portion istriggered at the beginning and end of said defined angle of rotation,and to perform an addition of a plurality of recorded images, eachincluding the plurality of illuminations for inspection for defects. 2.A method according to claim 1, wherein the selected portion is thefinish portion of the glass container.
 3. A method according to claim 2,wherein the defect is a check.
 4. A method according to claim 1, whereinsaid angle of rotation is a portion of 360 degrees.
 5. A methodaccording to claim 1, wherein said light sources comprises a pair oforthogonal related LED panels.
 6. A method according to claim 4, whereinsaid light source comprises a pair of orthogonal related LED panels. 7.A method according to claim 1, wherein the computer is configured todefine a critical addition of the plurality (Y) of recorded images,within a corresponding plurality of said defined angles (θ).
 8. A methodaccording to claim 7, wherein the imaging portion of the cameracomprises a matrix array of pixels which receives an image of theselected portion of the container, and wherein the critical additionincludes, for each pixel location of the matrix array, the highestintensity of the corresponding pixel in all (Y) recorded images withinthe plurality of said defined angles (θ).
 9. A method for inspecting aglass container for defects at an inspection station comprising:rotating a selected glass container at the inspection station;illuminating a selected portion of the glass container with a lightsource so that defects will be highlighted during the rotation of theglass container, the light source having a selected on time followed bya selected off time, wherein the container rotates through a definedangle of rotation while the light source is successively on and off;turning the light source on and off consecutively; imaging the selectedilluminated portion of the glass container with a camera including atriggerable imaging portion, the camera having an exposure time at leastequal to the time required for the glass container to rotate through thedefined angle of rotation; triggering the imaging portion of the camerawith a camera switch when the container is at the beginning and the endof the defined angle of rotation so that the camera will image theselected portion of the container, as the glass container rotatesthrough a defined selected angle of rotation, wherein the camera remainsopen during the entire selected angle of rotation and the camera switchis triggered a plurality of times to define a critical addition of theplurality of images, within the defined angle, for inspection fordefects; and configuring a computer to operate the light source switchand the camera switch, the computer being configured to trigger theimaging portion of said camera when the container is at the beginningand end of said defined angle of rotation so that the camera willcontinuously acquire data of said selected portion of the container, asthe glass container rotates through the defined angle of rotation tocapture, transfer and record each image when the imaging portion istriggered at the beginning and end of each of said defined angles ofrotation, and to perform an addition of a plurality of recorded images,each including a plurality of illuminations for inspection for defects,the plurality of illuminations equal to the number of times the lightsource switch is operated during the defined angle of rotation.
 10. Amethod according to claim 9, wherein the selected portion is the finishportion of the glass container.
 11. A method according to claim 9,wherein the defect is a check.
 12. A method according to claim 9,wherein the angle of rotation is a portion of 360 degrees.
 13. A methodaccording to claim 9, wherein the light source comprises a pair oforthogonal related LED panels.